Design of compact Wilkinson power divider and branch line coupler using hairpin based line

Abstract

In this paper hairpin unit based compact quarter wavelength line is proposed in order to miniaturize the Wilkinson power divider (WPD) and hybrid branch line coupler (HBLC). The proposed line consists of two series lines and a hairpin unit (HPU) in between them. The proposed line provides significant size reduction due to high slow-wave factor. The electrical lengths and impedances of the HPU are adjusted to produce two transmission zeros (TZs) above the operating frequency. These TZs are tuned to get good selectivity as well as suppress the harmonics. The proposed line is further utilized to design a compact WPD and HBLC operating at 1.5 GHz. The dimensions of those are 0.06λg × 0.184λg and 0.06λg × 0.25λg, respectively, where λg is the guided wavelength. A significant size reduction of 55% and 70% are obtained for WPD and HBLC, respectively, as compared to reference one at 1.5 GHz. The proposed designs (WPD and HBLC) are analyzed, fabricated and tested.